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Thread: Top Tube Length

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    Top Tube Length

    Talk to me about why I should worry about whether the top tube is comfortable on a bike. After all, you can get a suitable stem length to place the bars in a comfortable riding position. Why would I compromise the stand over height to get a particular top tube length?

    So, to keep this on-topic C&V, it pertains to looking for a new, old frame.

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    If the bike is to small you put a longer stem on but this changes the center of gravity and the balance of the bike if you are not centered to the bike it doesnt handle as well. If the bike is to small your inseam doesn't change so this raises the seat and your center of gravity and usually the handlebars can't come up far enough to balance out the height, bad back. Bike to big then you just lay on the top tube and your going to still raise the seat up for leg length but might not be able to get a stem short enough to be comfortable on this bike and the center of gravity is a lot higher, like monster trucks. But more important was that the old bikes came in 2" increments instead of 2 CM increments and the designed top tube length didn't really matter until Greg Lemond's book on fit, manufactures really start(caring) paying attention to top bar length, crank length,stem length and now women specific designed bikes by Trek Specialized ect..

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    Iconoclast rat fink's Avatar
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    Generally, the top tube and head tube lengths will be proportionate on a given size. On some frames, generally race geo frames with short chain stays, having your COG further back will result in suboptimal handling. The bike will feel skittish and wheelie easily on hills.
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    Quote Originally Posted by Mike Mills View Post
    Talk to me about why I should worry about whether the top tube is comfortable on a bike. After all, you can get a suitable stem length to place the bars in a comfortable riding position. Why would I compromise the stand over height to get a particular top tube length?

    So, to keep this on-topic C&V, it pertains to looking for a new, old frame.
    I never stop a bike and put two feet on the ground. Once I am underway, I am no longer concerned how far the top tube is below the saddle. Odd handling or reach will torment me every second of the ride.
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    Dave Moulton has an interesting discussion on frame size that might add to the discussion:
    http://davesbikeblog.squarespace.com...me-sizing.html

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    Quote Originally Posted by SJX426 View Post
    Dave Moulton has an interesting discussion on frame size that might add to the discussion:
    http://davesbikeblog.squarespace.com...me-sizing.html
    I think Moulton's statement that "the foot becomes an extension of the leg" has merit.

    +1 to ftwelder's comment.
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    Bianchi Goddess Bianchigirll's Avatar
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    I am still pretty old school on this. I feel on Sport, sport racing and Pro level bike the manufacturer has made the TT proportional to the ST for the average rider. so is the ST/standover is correct I feel the TT should be very close. if you have a super long torso, or ape like arms then your not average, and then you need either to sacrifice standover height for a longer TT or suffer with a freakishly long stem.

    I think this why most of gravitate to a particular brand or style of bike. we have others but we know when we see a Pinarello Sprint in a 57 c2c for example we know and can imagine how it will feel.
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    Designer steppinthefunk's Avatar
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    In my case as a short rider (5'4") top tube length is much more important than seat tube length.
    You would think that as a short guy I would be more concerned about stand over height but as it turns out,
    too many small frames have a much longer top tube than seat tube. Minimum top tube length is going to be about 52cm
    on a 700c frame. So even if a short rider was going to get a 48cm frame they still might end up with a bike
    that is 4cm too long in the top tube - try to compensate with a shorter stem and you end up with a rediculously short 50mm stem.

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    Good discussion. I look at it this way. Standover height and seat height go to leg length. TT length corresponds to torso length. Stem length and bar height are related to arm length. So, for me, my ideal bike geometry is ST 56-57, TT 555, stem 110-120.

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    Fuji Fan beech333's Avatar
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    I have a long torso, long arms, relatively short legs. I'm 6' with a wingspan of 6'2" and 32.5" inseam, just to give you an idea of my build. For me:

    58 ST & 56 TT = sporty/go fast
    58 ST & 58 TT = maximum comfort, but slower

    generally speaking, of course.

    I've found that the longer TT seems to smooth out the ride considerably and make me more comfortable for longer rides, but at a fairly high cost of speed. I try not to use longer stems than I already have because it messes with the steering too much.

    I'll be trying my first 60 x 59 frame as soon as it warms up.
    Last edited by beech333; 02-03-11 at 11:40 AM. Reason: typo. correction on leg length
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    To follow beech333's here are my measurements. 5'8.25"(no shoes), 6'1" wingspan, 30" inseam(no shoes), 22" sleeve(shoulder to palm) and size 11 shoes. (Yes, my knuckles get scarred from dragging the ground)

    I think what this shows is that everyone is different. You can use these charts such as Moulton's as a starting point but must find what works for you. That may or may not be the brands you desire or covet.

    So +1 to Bianchigirll's I think this why most of gravitate to a particular brand or style of bike. we have others but we know when we see a Pinarello Sprint in a 57 c2c for example we know and can imagine how it will feel.

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    Senior Member bobbycorno's Avatar
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    And no, you can't always get a stem long enough to compensate for a short top tube. Case in point: Raleigh Competition GS. 65 cm frame, 57 cm top tube. I normally ride a 61cm top tube and 11 cm stem. (And I'm about average proportions for my height) On the Comp GS, that would require a 15 cm stem. Ever seen a road stem in that length? Neither have I. And if it did exist, the weight distribution and steering would be a nightmare. On the whole standover issue, how much time do you spend standing over your bike vs riding it? I'd reverse your original question: why compromise fit for standover height?

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    Quote Originally Posted by SJX426 View Post
    Dave Moulton has an interesting discussion on frame size that might add to the discussion:
    http://davesbikeblog.squarespace.com...me-sizing.html
    Can't get to that from work, but BITD, Dave's sizing would've put me on a 61x57, IIRC. I normally ride a 64x61 or 65x60 with an 11-12cm stem, and bar ~1" below the saddle. Back in my racing days it was 63x59 with a 12-13cm stem and 4" saddle-to-bar drop. And no, I'm not oddly proportioned: 6'3", 36.5" inseam, 36" sleeve. Most production bikes fit me just fine, long as I can get one big enough. For some reason, tho', Brit bikes tend to be WAY too short in the top tube for my size. No idea why.

    SP
    Bend, OR

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    Quote Originally Posted by Mike Mills View Post
    Talk to me about why I should worry about whether the top tube is comfortable on a bike. After all, you can get a suitable stem length to place the bars in a comfortable riding position. Why would I compromise the stand over height to get a particular top tube length?

    So, to keep this on-topic C&V, it pertains to looking for a new, old frame.
    Top tube length is one component, but "set back" or seat tube angle also play a part.
    I laughed out loud when Richard Sachs advised on the CR list long ago that he gave Nasagawa complete freedom on design when building a bike for him as Richard said he specified set back only, and I imagine provided key body measurements or a seat tube length. Stating a set back essentially locked in the frame design as to seat tube angle.

    A slack seat tube angle when not needed or wanted by the rider to get the best position effects top tube length just as dramatically as tube length.

    In addition, a short top tube that required a long stem for god position places more weight on the front wheel, which may or may not be wanted.

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    Designer steppinthefunk's Avatar
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    If I were a bike builder looking to mass produce I would make a bunch of square geometry sizes off the peg.

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    Because

    Quote Originally Posted by bobbycorno View Post
    On the whole standover issue, how much time do you spend standing over your bike vs riding it? I'd reverse your original question: why compromise fit for standover height? SP Bend, OR
    on that one emergency occasion (and
    I am willing to concede it may never
    happen) when I need to get "off the
    seat and on my feet" in a hurry --
    I would like to be able to continue
    singing the alto parts in choir practice.

    I'm just not well suited to soprano vocal
    lines.
    Quote Originally Posted by Terrierman View Post
    No wonder everybody hates you.

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    Quote Originally Posted by bobbycorno View Post
    And no, you can't always get a stem long enough to compensate for a short top tube.
    This is part of the reason of why I will never get a Fuji Finest. As much as I love the look of the blue ones, the ultra short TT will never work for me.

    1. I wouldn't trust the integrity of a long enough stem to make it fit.
    2. The bike would look silly with such a long stem.
    3. The long stem would jack up the steering.

    http://classicfuji.com/1974_04_Finest_PageB.htm
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    Several interesting points here. Top tube length is a funny dimension. I find that it's most relevant when considering it's length forward of the BB center line. For example, If I were to to measure the top tubes on two of my most ridden bikes: The fuji is a 54cm with a 55cm top tube. The Colnago is a 57cm with a 57cm top tube. However, measured forward of the bottom bracket, the Colnago's top tube is .5cm shorter than the fuji's top tube. This means that, even though the Colnago frame is larger, the Fuji frame creates more overall reach. That happens because the Colnago has a slacker seat tube angle of 73.5 and the Fuji utilizes an STA of 75 degrees. Using a seat post with a 1cm offset on the Fuji, and using a no offset/setback seat post on the Colnago, allows both bikes to have achieve the same saddle position at a saddle height of 79cm from the BB center line and effectively negates the difference in top tube and seat tube angles with the exception of that .5cm.
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    Quote Originally Posted by seypat View Post
    To follow beech333's here are my measurements. 5'8.25"(no shoes), 6'1" wingspan, 30" inseam(no shoes), 22" sleeve(shoulder to palm) and size 11 shoes. (Yes, my knuckles get scarred from dragging the ground)

    I think what this shows is that everyone is different. You can use these charts such as Moulton's as a starting point but must find what works for you. That may or may not be the brands you desire or covet.

    So +1 to Bianchigirll's I think this why most of gravitate to a particular brand or style of bike. we have others but we know when we see a Pinarello Sprint in a 57 c2c for example we know and can imagine how it will feel.

    Those are VERY similar to my own measurements. I need a 50cm seat tube to have any substantial standover but I'm most comfortable with a TT length of about 55.5cm + 10cm stem. I've ridden bikes that are "too big" for me to get this TT measurement and usually don't mind, but for a cross bike and city commuter I NEED standover....

    I'm actually at a standstill building my frame because I can't figure out how to get a 50-52cm seat tube, 55.5cm top tube, a high bb and still have a horizontal top tube. I've been meaning to post a question about this in the framebuilders section....off I go
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    Very interesting topic. I just measured all my bikes this past weekend. There was quite a bit of variation - but the two most comfortable measured at 53 and 54 c-t-c on the seat tube and 55 c-t-c on the top tube. I'm 5'9" with a 30 inch inseam and a little longer torso. My Gitane Sprint that I love to ride is a little tougher to get right and I've just gone to a longer stem - it's 51 cm c-t-c and 53 c-t-c respectively.

    When I got the 56 cm Trek I was more concerned with top tube length and standover height. Turns out the top tube is the same as the seat tube and my comfort was fine with the shorter stem that was on it - which in my mind makes sense.

    Slowly I'm figuring out what my "optimal" fit should be.
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    Quote Originally Posted by beech333 View Post
    This is part of the reason of why I will never get a Fuji Finest. As much as I love the look of the blue ones, the ultra short TT will never work for me.

    1. I wouldn't trust the integrity of a long enough stem to make it fit.
    2. The bike would look silly with such a long stem.
    3. The long stem would jack up the steering.

    http://classicfuji.com/1974_04_Finest_PageB.htm


    my measurements:

    6'3", 33-34" inseam, very long in torso.

    I'm very comfy on the bike, though it is a little more upright than usual so maybe that's why.

    I'm also very comfy on this, and I think the center of the seat post to the bars is about the same in the end.

    Mmmm, bicycles.

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    Yes, very interesting discussion here and that link to Moulton's blog is a good contribution. Are there any other frame builder who have talked to this subject? Anyone have links?

    I will be going home tonight and will measure all my top tubes and compare to the data given herein. I am "long waisted" and have fairly long arms (36" sleeve length). All my bikes (race or mountain) seem to have 110 mm stems in them.

    For me, I want some clearance when standing over the top tube. I, for one, have had to get "off and out" fast and came down hard on a too high top tube. NEVER AGAIN! I need some margin, some space. This is why I am primarily concerned about seat tube rather than top tube. One reson is that (I presume here) most top tubes are adequate for most people and the small changes (within reason) needed to fit an individual are acceptably made via the stem.

    Having said all that, when I get home tonight, I will measure my bikes, reread and digest this thread and see where I am relative to the guideleines given.

    Keep the comments coming, guys and girls.
    Last edited by Mike Mills; 02-03-11 at 06:33 PM.

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    Don't measure your top tube--measure the distance from the nose of your saddle to the middle of the stem clamp. Try that measurement on various bikes. Assuming the saddle is of similar size on each, take a look at the one bike that feels most "right" to you.

    As far as coming down hard on top tubes, guess you could wear a protective cup or something.

    Neal

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    Interesting discussion. I still don't grasp TT length very well. Then again, I just try to understand what I like and then replicate it on most of my bikes by varying the stem length. Here are the sizes of some of my bikes:

    Data is presented as Bike model: ST (c-c), TT (c-c), stem length (in cm)

    All have drop bars except the Jeunet

    Trek 560_____________60, 57, 10
    Raleigh Comp GS______59, 56, 11
    Jeunet 630____________62, 59, 10 (upright city bars)
    Shogun 2000__________57, 55, 10 (too small)
    Shogun 1500__________62, 57, 10
    Schwinn Voyageur______62, 57, 10

    If you add the TT and stem lengths for these bikes you get:

    67
    67
    69 (upright city bars)
    65 (too cramped for me)
    67
    67

    As you can see, 67 cm combined TT+stem length is the sweet spot for me. I don't know my torso or arm length, but I'm 6'1" with a 34" inseam.

    I agree with some of the above comments that using too long of a stem (>110mm) may cause steering instability. I still don't grasp that very well, either, but I guess that in addition to moving your center of gravity closer to the front wheel, it also introduces more lateral movement of the bars as you turn them. I don't know if this is significant, but in theory it seems like it could affect the handling.
    Last edited by southpawboston; 02-03-11 at 04:45 PM.
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    A stem longer than 110 mm is actually a rarity. I went looking for one recently and came up almost empty handed.

    It is important to remember that things like top tube and stem length vary by only a small amount (10's of millimeters) unless you consider "funny bikes" and circus clowns.

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